Carburetor fuel feeding device



Jan. 28, 1958 E. OLSON 2,821,373

' CARB'URETOR FUEL FEEDING DEVICE Filed April 30, 1956 Vacuum. x(vemuri)ATTORNEY INVENTOR I United States Patent CARBURETOR FUEL FEEDING DEVICEElmer Olson, Rochester, N. Y., assignor to General Motors Corporation,Detroit, Mich.,' a corporation of Delaware Application April 30, 1956,Serial No. 581,597

2 Claims. (Cl. 261-78) The present invention relates to an improved fuelfeeding device for a carburetor. More specifically, the presentinvention relates to means whereby the transition from idling to normalfuel feed flow is made more smoothly particularly under light throttleloading.

It has been found that in progressing from idle to normal operationunder light throttle loading, the air flow through the conventionalbooster venturi is too low to create enough vacuum to adequately startthe flow of fuel through-the main fuel nozzle. Accordingly, the engineis starved for fuel with a consequent fall-off in power until such timeas the throttle is opened sufiicient- 1y to increase air flowthrough'the induction passages and in turn increase the booster venturivacuum.

It is the purpose of the present invention to provide a device for morequickly starting the flow of fuel through the main fuel nozzle under lowair flow conditions as during the aforementioned transition from idlingto normal running conditions. Pursuant to this purpose a vacuummultiplying means has been developed which can replace the conventionalbooster venturi.

A description of the present invention is hereinafter set i forth indetail.

. In the drawings:

Figure 1 is a fragmentary sectional elevation of a carburetor embodyingthe improved fuel feeding device.

Figure 2 is a' fragmentary showing of a conventional booster venturi.

Figure 3 is a graphic representation of a typical carburetor flow curve.

Figure 4 is a graphic comparison of the vacuum obtainable with thesubject device as compared with a conventional venturi of the type shownin Figure 2.

Referring to the fragmentary view of a carburetor shown generally at 10in Figure 1, a casing 12 includes a fuel bowl 14, and a main fuel well24. Well 24 is interconnected with the fuel bowl through a restrictedpassage formed in a plug 16. A portion of an induction passage 18 isformed in casing 12 and includes a main venturi 20 having a throat 22.

A throttle body casing is shown at 26 and includes a throttle valve 28,as well as the remaining portion of induction passage 18.

Usually formed separately from casing 12 but mounted thereon is a fuelsupplying casting or cluster 30. Cluster 30 is mounted super-adjacentthe main fuel well 24 and dependingly supports a fuel nozzle 32. Nozzle32 is of sufficient length to extend below the normal fuel level in well24. Nozzle 32 is suitably perforated below the fuel level to permit fuelto flow interiorly thereof.

The upper or supported end of nozzle 32 projects with in an aspiratingpassage 36 and terminates in a bevelled portion 38 which, as will behereinafter explained, opens downwind with respect to normal airflow.Passage 36 is open to substantially atmospheric pressure at end 40 whichactually communicates with the induction passage 18 anterior of the mainventuri 20. The other end of passage 36 is, under normal operatingconditions, ex-

posed to sub-atmospheric pressures, therefore, air flows from end 40past the bevelled portion 38 of fuel nozzle 32 into the main venturi 20.

Air in thus flowing through the passage 36 has an aspirating or eductingeffect on the nozzle 32 causing the fuel therein to be drawn intopassage 36 at a rate proportional to the velocity of air flow throughsaid passage. The fuel is, of course, mixed with air in aspiratingpassage 36 to provide, what is at this point, an over-rich mixture offuel and air to the main venturi entrance.

In order to provide an adequate supply of fuel to the main venturi 20,it is normal practice to provide means to insure that the velocity ofair flow through passage is sufficient for normal operating conditions.Referring momentarily to Figure 2 in conjunction with the generalenvironment of Figure 1, this air flow has normally been assured by theprovision of a booster or auxiliary venturi 44 which is supported fromthe inner end of passage 36' and projects centrally within the upper endof the main venturi 20. I

Under normal operating conditions the flow of air through boosterventuri 44 creates sufficient sub-atmospheric pressure or vacuum in theventuri end of passage 36 to insure an adequate supply of fuel. It hasbeen found, however, that during conditions of low air flow through theinduction passage 18, particularly as occurs during the transition fromidling to normal operating conditions With throttle 28 only partiallyopen, the booster venturi does not provide sufficient vacuum to draw therequisite amount of fuel through the main nozzle 32 for smooth engineoperation. As a consequence, the engine is starved for fuel and there isa perceptible drop off in power until the situation is rectified byfurther throttle opening. I

This condition. canbe. graphically represented in Fig ure 3 in which aportioniof a typical carburetor flow curve is represented at 48. In thiscase air-fuel ratio- A/Fis plotted against airflow. The portionof curve48 between lines A and B is intended to illustrate the part of thecurve. theoretically involved in making ,th e transi; tion from idle tonormal operation. As already noted, however, under light throttleloading with a conventional booster venturi, air and fuel flow arequantitatively reduced to an amount which results in a sag, indicated bybroken line 50, below the normal curve portion AB. The sag isfunctionally manifested in the loss of power already referred to above.

It is to eliminate this loss of power under the frequently occurringconditions noted, that the present invention is dedicated. Havingdetermined the cause for the loss of power, particularly during thetransition from idle to normal operation with light throttle loading, anovel vacuum multiplying mechanism 60 has been developed, a preferredform of which is shown in Figure 1.

Mechanism 60 is intended when necessary to replace the traditionalbooster of the type shown and described in relation to Figure 2.Mechanism 60 is designed particularly to provide a relatively highvacuum during conditions of low air flow.

The vacuum multiplying mechanism 60 includes a cylindrical sleeve 62formed integrally, or otherwise supported, upon passage 36. The sleeve62 has open ends 64 and 66 aligned in the direction of air flow throughinduction passage 18. End 66 of sleeve 62 extends with in venturi 20 andterminates proximate throat 22 thereof. It has been found preferable toprovide the inner wall of sleeve 62 with a slight restriction at 68 justposterior of the junction of the sleeve with passage 36. The portion ofthe inner Wall of sleeve 62 posterior of restriction 68 is slightlydivergent. The inner wall anterior of restriction 68 as well as theouter wall are substantially cylindricalv "To insure the relatively highvacuum, referred to above,

is substantially diametrically co-extensive with end. 64

of sleeve 62, in a smoothly curving fashion to terminate in a restrictedportion 74 proximate sleeve restriction 68.

As thus constructed and arranged, the inner end of passage 36, sleeve 62and nozzle 70 cooperate to define a downwardly opening annular vacuumchamber 78'. Further, the smoothly curving entrance of nozzle 70relatively efiiciently converts the pressure head of air flowingtherethrough to a velocity head. Unlike a venturi which again graduallydiverges from the restricted portion or throat, nozzle 70 discharges thehigh velocity air into the appreciably and abruptly larger sleeve 62with a resultant high turbulence and correspondingly high eductiveeffect on chamber 78 and creating therewithin a relatively high vacuumeven through the quantitative flow of air through the nozzle may be low.

The result of this novel arrangement is to insure a higher vacuum and aconsequently greater quantity of fuel fiow under low air flow conditionsthan is possible with a conventional secondary or booster venturi.

The difference in the vacuum obtainable under the conditions set forthisillustrated graphically in Figure 4 in which vacuum is plotted againstair fiow. Curves X and Y respectively depict in a general way thevacuumair flow relationships through a venturi and through the subjectnozzle. Again the lines A and B depict the portions of the curvesinvolved during the transition from idle to normal operation under lightthrottle loading. It will thus be seen that between A and B a highervacuum is realizable for a given air flow with the subject nozzle thanis the case with a venturi.

Inasmuch as nozzle 70 is preferably an insertable member which isadapted to be removably mounted in sleeve 62, it is apparent thatnozzles of the general type shown but having different flowcharacteristics may be utilized 7 in a given carburetor. In this way, itis possible to more closely match nozzle characteristics with aparticular engine. Further, the versatility of the present fuel feedingdevice is greatly enhanced as well as providing a simply andinexpensively manufactured sub-assembly.

I claim:

1. A carburetor comprising an induction passage, venturi means in saidpassage, a fuel bowl, a perforate nozzle projecting within said fuelbowl, passage means communicating said nozzle with said venturi, and afuel cluster, said fuel cluster including a mixture passage connected atone end with said nozzle and terminating at the other end in anopen-ended cylindrical sleeve disposed within said venturi, said sleevebeing disposed centrally of said venturi and having one of its open endsterminating proximate the venturi throat, said sleeve having a portionof reduced cross-section posterior to the junction of said sleeve andfuel passage, and a nozzle supported from the other end of said sleeveand projecting therewithin in radially spaced relation to the inner wallof said sleeve, the other end of said nozzle terminating adjacent thereduced portion of said sleeve.

2. A carburetor comprising an induction passage, venturi means in saidpassage, a fuel bowl, a perforate nozzle projecting within said fuelbowl, passage means communicating said nozzle with said venturi and afuel cluster, said fuel cluster including a mixture passage connected atone end with said nozzle and terminating at the other end in anopen-ended sleeve disposed within said venturi, said sleeve beingdisposed centrally of said venturi and having an internal portion ofreduced cross section posterior to the junction of said sleeve and fuelpassage, and a tapered nozzle supported from the anterior end of saidsleeve and projecting therewithin in radially spaced relation to theinner wall of said sleeve, the most restricted end of said nozzleterminating proximate the reduced portion of said sleeve.

References Cited in the file of this patent

